This invention claims the benefit of Japanese Patent Application No. HEI 11-82056, filed on Mar. 25, 1999, which is hereby incorporated by reference.
1. Field of the Invention
The invention relates to a lamp for use in the illumination of a headlamp, etc., and more particularly relates to a vehicle lamp forming a light distribution characteristic in a multi-reflex manner using an ellipse group reflector and a parabola group reflector.
2. Description of the Related Art
FIG. 8 shows an example configuration for a vehicle lamp fitting 90 for use in a conventional headlamp. Here, a light source 92 having a filament such as C-6 or C-8 type (an example of a C-6 type is shown in the FIG. 3) is positioned approximately at the focal point of a reflector 91 that includes a parabola group surface such as a rotated paraboloid, a parabolic surface, or a free-curved surface. The dimensions of such a reflector 91 are a width w of approximately 150 to 300 mm, and a height h of approximately 80 to 150 mm.
In the vehicle lamp fitting 90, when the C-6 type filament is used as the light source 92, it is difficult to prevent all unnecessary upwardly inclined light from being emitted toward the on-coming lane. In recent years it has therefore become common to adopt a C-8 type filament provided with a hood within a bulb (H-4 type) for preventing light from being directed toward the lower half of the reflector 91. However, in this case the vehicle lamp fitting 90 has a decreasing rate of utilization of the luminous flux due to the hood within the bulb.
It is important that the characteristics of the reflector 91 of the vehicle lamp fitting 90, such as the aspect ratio, etc., match with the design of the vehicle to which the vehicle lamp fitting 90 is to be attached. Accordingly, so-called oblong designs where the width w is smaller than the height h of the lamp may be required.
However, since a broad light distribution pattern in a widthwise direction is preferable in this type of vehicle lamp fitting, when the width w necessary for maintaining the preferred amount of light in the horizontal direction is narrowed, the amount of light emitted by the vehicle lamp noticeably decreases. For example, when the width w is narrowed to approximately 50 mm, only half the amount of light as compared to the related art is obtained, and the remaining light cannot be put to practical use.
In particular, when a C-8 type filament is used as the light source 92 and the width of the vehicle lamp fitting is narrowed, the hood no longer functions properly. The loss of light due to the decrease in the width of the lamp is not consistent with and deteriorates the function of the hood, which is provided to prevent upwardly inclined light from being emitted from the vehicle lamp. As a result, the light distribution and amount of light produced by the lamp deteriorate. In all of the above mentioned cases, an oblong design cannot be implemented without causing serious deterioration of the light quality of the lamp, which in turn puts limitations on the design of the vehicle body.
In order to resolve the aforementioned problems in the related art, the invention includes an oblong headlamp that has an ellipse group first reflector, a parabolic group second reflector, an ellipse group third reflector and a parabolic group fourth reflector. A light source can be located at a first focal point of the ellipse group first reflector. The parabolic group second reflector has a focal point located in the vicinity of a second focal point of the first reflector. The light source is also located at a first focal point of the ellipse group third reflector. The parabolic group fourth reflector has a focal point located in the vicinity of the second focal point of the third reflector. The second focal point of the first reflector is located above the first focal point and the second reflector is located above the first reflector. The second focal point of the third reflector is located below the first focal point, and the fourth reflector is located below the third reflector. The first reflector and third reflector share a light source at a respective first focal point.
An aperture can be provided in part of the first reflector and/or part of the third reflector, and a parabolic group fifth reflector can be provided for directing light that has been emitted from the light source and which has traveled through the aperture, in a direction of illumination of the oblong headlamp. In other words, light reflected by the fifth reflector in the illumination direction of the vehicle lamp originated from the light source and passed through the aperture in the first reflector.
The third reflector can also be divided into a front third reflector and a rear third reflector and the fourth reflector can be divided into a front fourth reflector and a rear fourth reflector. The front third reflector mainly directs light going downwards and forwards from the light source toward the rear fourth reflector, and the rear third reflector mainly directs light going downwards and forwards from the light source toward the front fourth reflector. The rear third reflector and front fourth reflector mainly direct light toward an illumination direction of the oblong headlamp.
The invention can include only the upper half (i.e. the first and second reflectors) or the lower half (i.e. the third and fourth reflectors) of the aforementioned oblong headlamp.